MOCVD Growth and Characterization of InNAs/GaAs Quantum Wells
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MOCVD Growth and Characterization of InNAs/GaAs Quantum Wells Abdel-Rahman A. El-Emawy1, Noppadon Nuntawong1, Hongjun Cao1, Chiyu Liu1, Huifang Xu2, and Marek Osin´ski1 1 Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106-4343, U.S.A. 2 Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A. ABSTRACT InNAs/GaAs multiple-quantum-wells were grown by MOCVD on (100) SI-GaAs substrates using trimethylindium, tertiarybutylarsine, and 95-97.5% of dimethylhydrazine (DMHy) in the vapor phase. The crystalline quality and solid phase composition were evaluated using highresolution x-ray diffraction analysis. Nitrogen content in InNAs wells was determined to be 28%. Electron energy loss spectroscopy was used to confirm the presence of nitrogen in quantum wells. Surface morphology was investigated by atomic force microscopy (AFM) and field emission microscopy (FEM). INTRODUCTION The InNxAs1-x alloy is a very promising material for mid-infrared (2-8 µm) emitters and detectors. With a single exception of recently reported successful growth of InNAs by MOCVD with plasma cracked ammonia source [1], all studies of InNAs growth utilized plasma-source MBE [2]-[4] and related techniques, such as gas-source MBE [5], [6]. In this paper, we report a successful MOCVD growth of InNAs by using for the first time the uncracked dimethylhydrazine (DMHy) as the nitrogen source. As with other dilute nitrides, the bandgap of InNxAs1-x was predicted to shrink with increasing nitrogen content x [6-9]. This has been confirmed experimentally for compositions x < 6% [6], and 18% [9]. The InNxAs1-x alloy can be lattice-matched to GaAs when x = 38% [2]. The large band offset between this material and GaAs barriers makes it particularly attractive for reducing temperature sensitivity of mid-IR lasers. Since the solubility limit of nitrogen in InAs is among the highest among binary III-V compounds (3 orders of magnitude higher than in GaAs, for example) [10], we considered it feasible to attempt the low temperature growth using DMHy. In this paper we investigate the structural properties of InNAs/GaAs quantum wells as a function of different growth parameters. EXPERIMENTAL DETAILS All samples were grown in a Thomas Swan vertical MOCVD reactor at 60 Torr. Arsine and trimethylgallium were used during the growth of GaAs buffer, barrier, and cap layers. InNAs films were grown using trimethylindium, tertiarybutylarsine and DMHy as source materials. Before the growth, epi-ready (100) SI-GaAs substrates were deoxidized at 760 °C for 5 minutes. 300 nm GaAs buffer layer was grown at 680 °C. Then the temperature was lowered to 460 - 500 °C for the growth of InNAs/GaAs multiple quantum well (MQW) structures and the GaAs capping. Typical growth rate was 7.5 Å/s and 0.57Å/s for GaAs and InNAs films, respectively.
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The mole fraction of DMHy to total group-V sources in the vapor phase was maintained between 0.95 and 0.975, corresponding to DMH
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